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+;;; mldrag.el -- Mode line and vertical line dragging to resize windows.
+;;; Copyright (C) 1994 Free Software Foundation, Inc.
+
+;; Author: Kyle E. Jones <kyle@wonderworks.com>
+;; Keywords: mouse
+
+;; This file is part of GNU Emacs.
+
+;; GNU Emacs is free software; you can redistribute it and/or modify
+;; it under the terms of the GNU General Public License as published by
+;; the Free Software Foundation; either version 2, or (at your option)
+;; any later version.
+
+;; GNU Emacs is distributed in the hope that it will be useful,
+;; but WITHOUT ANY WARRANTY; without even the implied warranty of
+;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+;; GNU General Public License for more details.
+
+;; You should have received a copy of the GNU General Public License
+;; along with GNU Emacs; see the file COPYING.  If not, write to
+;; the Free Software Foundation, 675 Mass Ave, Cambridge, MA 02139, USA.
+
+;;; Commentary:
+
+;; This package lets you drag the modeline, vertical bar and
+;; scrollbar to resize windows.  Suggested bindings are:
+;;
+;;   (global-set-key [mode-line down-mouse-1] 'mldrag-drag-mode-line)
+;;   (global-set-key [vertical-line down-mouse-1] 'mldrag-drag-vertical-line)
+;;   (global-set-key [vertical-scroll-bar S-down-mouse-1]
+;;                   'mldrag-drag-vertical-line)
+;;
+;; Put the bindings and (require 'mldrag) in your .emacs file.
+
+;;; Code:
+
+(provide 'mldrag)
+
+(defun mldrag-drag-mode-line (start-event)
+  "Change the height of the current window with the mouse.
+This command should be bound to a down-mouse- event, and is most
+usefully bound with the `mode-line' prefix.  Holding down a mouse
+button and moving the mouse up and down will make the clicked-on
+window taller or shorter."
+  (interactive "e")
+  (let ((done nil)
+	(echo-keystrokes 0)
+	(start-event-frame (window-frame (car (car (cdr start-event)))))
+	(start-event-window (car (car (cdr start-event))))
+	(start-nwindows (count-windows t))
+	(old-selected-window (selected-window))
+	should-enlarge-minibuffer
+	event mouse minibuffer y top bot edges wconfig params growth)
+    (setq params (frame-parameters))
+    (if (and (not (setq minibuffer (cdr (assq 'minibuffer params))))
+	     (one-window-p t))
+	(error "Attempt to resize sole window"))
+    (unwind-protect
+	(track-mouse
+	  (progn
+	    ;; enlarge-window only works on the selected window, so
+	    ;; we must select the window where the start event originated.
+	    ;; unwind-protect will restore the old selected window later.
+	    (select-window start-event-window)
+	    ;; if this is the bottommost ordinary window, then to
+	    ;; move its modeline the minibuffer must be enlarged.
+	    (setq should-enlarge-minibuffer
+		  (and minibuffer
+		       (not (one-window-p t))
+		       (= (nth 1 (window-edges minibuffer))
+			  (nth 3 (window-edges)))))
+	    ;; loop reading events and sampling the position of
+	    ;; the mouse.
+	    (while (not done)
+	      (setq event (read-event)
+		    mouse (mouse-position))
+	      ;; do nothing if
+	      ;;   - there is a switch-frame event.
+	      ;;   - the mouse isn't in the frame that we started in
+	      ;;   - the mouse isn't in any Emacs frame
+	      ;; drag if
+	      ;;   - there is a mouse-movement event
+	      ;;   - there is a scroll-bar-movement event
+	      ;;     (same as mouse movement for our purposes)
+	      ;; quit if
+	      ;;   - there is a keyboard event or some other unknown event
+	      ;;     unknown event.
+	      (cond ((integerp event)
+		     (setq done t))
+		    ((eq (car event) 'switch-frame)
+		     nil)
+		    ((not (memq (car event)
+				'(mouse-movement scroll-bar-movement)))
+		     (setq done t))
+		    ((not (eq (car mouse) start-event-frame))
+		     nil)
+		    ((null (car (cdr mouse)))
+		     nil)
+		    (t
+		     (setq y (cdr (cdr mouse))
+			   edges (window-edges)
+			   top (nth 1 edges)
+			   bot (nth 3 edges))
+		     ;; scale back a move that would make the
+		     ;; window too short.
+		     (cond ((< (- y top -1) window-min-height)
+			    (setq y (+ top window-min-height -1))))
+		     ;; compute size change needed
+		     (setq growth (- y bot -1)
+			   wconfig (current-window-configuration))
+		     ;; grow/shrink minibuffer?
+		     (if should-enlarge-minibuffer
+			 (progn
+			   ;; yes.  briefly select minibuffer so
+			   ;; ealarge-window will affect the
+			   ;; correct window.
+			   (select-window minibuffer)
+			   ;; scale back shrinkage if it would
+			   ;; make the minibuffer less than 1
+			   ;; line tall.
+			   (if (and (> growth 0)
+				    (< (- (window-height minibuffer)
+					  growth)
+				       1))
+			       (setq growth (1- (window-height minibuffer))))
+			   (enlarge-window (- growth))
+			   (select-window start-event-window))
+		       ;; no.  grow/shrink the selected window
+		       (enlarge-window growth))
+		     ;; if this window's growth caused another
+		     ;; window to be deleted because it was too
+		     ;; short, rescind the change.
+		     ;;
+		     ;; if size change caused space to be stolen
+		     ;; from a window above this one, rescind the
+		     ;; change, but only if we didn't grow/srhink
+		     ;; the minibuffer.  minibuffer size changes
+		     ;; can cause all windows to shrink... no way
+		     ;; around it.
+		     (if (or (/= start-nwindows (count-windows t))
+			     (and (not should-enlarge-minibuffer)
+				  (/= top (nth 1 (window-edges)))))
+			 (set-window-configuration wconfig)))))))
+      ;; restore the old selected window
+      (select-window old-selected-window))))
+
+(defun mldrag-drag-vertical-line (start-event)
+  "Change the width of the current window with the mouse.
+This command should be bound to a down-mouse- event, and is most
+usefully bound with the `vertical-line' or the `vertical-scroll-bar'
+prefix.  Holding down a mouse button and moving the mouse left and
+right will make the clicked-on window thinner or wider."
+  (interactive "e")
+  (let ((done nil)
+	(echo-keystrokes 0)
+	(start-event-frame (window-frame (car (car (cdr start-event)))))
+	(start-event-window (car (car (cdr start-event))))
+	(start-nwindows (count-windows t))
+	(old-selected-window (selected-window))
+	event mouse x left right edges wconfig growth)
+    (if (one-window-p t)
+	(error "Attempt to resize sole ordinary window"))
+    (if (= (nth 2 (window-edges start-event-window))
+	   (frame-width start-event-frame))
+	(error "Attempt to drag rightmost scrollbar"))
+    (unwind-protect
+	(track-mouse
+	  (progn
+	    ;; enlarge-window only works on the selected window, so
+	    ;; we must select the window where the start event originated.
+	    ;; unwind-protect will restore the old selected window later.
+	    (select-window start-event-window)
+	    ;; loop reading events and sampling the position of
+	    ;; the mouse.
+	    (while (not done)
+	      (setq event (read-event)
+		    mouse (mouse-position))
+	      ;; do nothing if
+	      ;;   - there is a switch-frame event.
+	      ;;   - the mouse isn't in the frame that we started in
+	      ;;   - the mouse isn't in any Emacs frame
+	      ;; drag if
+	      ;;   - there is a mouse-movement event
+	      ;;   - there is a scroll-bar-movement event
+	      ;;     (same as mouse movement for our purposes)
+	      ;; quit if
+	      ;;   - there is a keyboard event or some other unknown event
+	      ;;     unknown event.
+	      (cond ((integerp event)
+		     (setq done t))
+		    ((eq (car event) 'switch-frame)
+		     nil)
+		    ((not (memq (car event)
+				'(mouse-movement scroll-bar-movement)))
+		     (setq done t))
+		    ((not (eq (car mouse) start-event-frame))
+		     nil)
+		    ((null (car (cdr mouse)))
+		     nil)
+		    (t
+		     (setq x (car (cdr mouse))
+			   edges (window-edges)
+			   left (nth 0 edges)
+			   right (nth 2 edges))
+		     ;; scale back a move that would make the
+		     ;; window too thin.
+		     (cond ((< (- x left -1) window-min-width)
+			    (setq x (+ left window-min-width -1))))
+		     ;; compute size change needed
+		     (setq growth (- x right -1)
+			   wconfig (current-window-configuration))
+		     (enlarge-window growth t)
+		     ;; if this window's growth caused another
+		     ;; window to be deleted because it was too
+		     ;; thin, rescind the change.
+		     ;;
+		     ;; if size change caused space to be stolen
+		     ;; from a window to the left of this one,
+		     ;; rescind the change.
+		     (if (or (/= start-nwindows (count-windows t))
+			     (/= left (nth 0 (window-edges))))
+			 (set-window-configuration wconfig)))))))
+      ;; restore the old selected window
+      (select-window old-selected-window))))
+
+;; mldrag.el ends here